1. Field of the Invention
This invention relates to a disk drive suspension comprising an actuator element.
2. Description of the Related Art
A hard disk drive (HDD) is used in an information processor such as a personal computer. The HDD comprises a magnetic disk rotatable about a spindle, a carriage turnable about a pivot, etc. The carriage comprises an actuator arm, and is configured to be turned transversely relative to tracks of the disk about the pivot by a positioning motor such as a voice coil motor.
A suspension is mounted on the actuator arm. The suspension comprises a load beam, and a flexure disposed to overlap the load beam. A slider, which constitutes a magnetic head, is mounted on a gimbal portion formed near a distal end of the flexure. The slider is provided with an element (transducer) for accessing data, that is, for reading or writing of data.
In order to deal with increased recording density of disks, it is necessary to position the magnetic head with higher precision with respect to the recording surface of the disk. In order to achieve this, as disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2002-50140 (Patent Document 1), dual-stage-actuator (DSA) suspensions, which use positioning motors (voice coil motors) together with actuator elements made of a piezoelectric material such as lead zirconate titanate (PZT), have been developed. With the DSA suspension, it is possible to quickly move a distal end of the suspension by an infinitesimal distance in a sway direction (or transversely relative to tracks) by applying a voltage to the actuator elements and thereby deforming the actuator elements. The actuator elements are disposed on an actuator mounting section provided in the suspension.
The element made of the piezoelectric material has a plate-like configuration, and is provided with an electrode on a surface at one side in a thickness direction and another electrode on a surface at the other side. The electrode on one side is electrically connected to a metallic plate via an electrically conductive paste, such as a silver paste. The electrode on the other side is connected to an interconnect member of a flexure via a conductive member, such as a bonding wire. As has been disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2010-146631 (Patent Document 2) and Jpn. Pat. Appln. KOKAI Publication No. 2010-218626 (Patent Document 3), DSA suspensions having an actuator element made of PZT, etc., mounted on a gimbal portion of a flexure are known.
At a terminal portion of the actuator element, a gold-plating layer is formed to improve conductivity with the electrically conductive paste. However, since gold is an inactive metal, adherence to the electrically conductive paste is not good. Accordingly, in a place where the gold-plating layer is provided, peel strength between the electrically conductive paste and the terminal portion may be weakened. For example, when a continuity test was conducted in high-temperature and high-humidity atmosphere, there were cases where electrical resistance between the terminal portion and the electrically conductive paste was increased, causing poor electrical connection to the actuator element. Thus, some came up with an idea of forming a roughening processed portion including a number of pits and projections on a surface of the gold-plating layer.
However, in a suspension comprising extremely small actuator elements, it has been found that the roughening treatment performed on a surface of the gold-plating layer sometimes adversely affects the adherence of the electrically conductive paste to the gold-plating layer in the terminal portion on the contrary. The reason for this has been studied intensely and the following is found out:
When an extremely small actuator is used, the terminal portion of the actuator element is extremely small, so that the thickness of a base nickel layer used as the base of the gold plating is also small. For this reason, when the power of the laser beam is too strong in performing the roughening treatment on the gold-plating layer or etching is excessive in performing the roughening treatment by etching, the base nickel layer is coarsened or a hole is formed, thereby exposing copper of a conductor in some cases. When the copper of the conductor is exposed, the copper surface is oxidized, which causes deterioration of wettability for the electrically conductive paste.